[R] selectively altering variable value
jim holtman
jholtman at gmail.com
Mon Aug 3 18:04:39 CEST 2009
This should set the first two ia==4 entries to 1 in saccade column:
> x <- read.table('/tempxx.txt.r', header=TRUE)
> x
vp trial ia saccade
1 1 1 5 0
2 1 1 5 0
3 1 1 5 0
4 1 1 5 1
5 1 1 5 1
6 1 1 9 1
7 1 1 9 1
8 1 1 9 1
9 1 1 4 1
10 1 1 4 0
11 1 2 5 0
12 1 2 5 0
13 1 2 5 0
14 1 2 5 1
15 1 2 5 1
16 1 2 9 1
17 1 2 9 1
18 1 2 9 1
19 1 2 4 1
20 1 2 4 1
21 1 2 4 0
22 1 2 4 0
23 1 3 5 0
24 1 3 5 0
25 1 3 5 0
26 1 3 5 1
27 1 3 5 1
28 1 3 9 1
29 1 3 9 1
30 1 3 9 1
31 1 3 4 0
32 1 3 4 0
33 1 3 4 0
34 1 4 5 0
35 1 4 5 0
36 1 4 5 0
37 1 4 5 1
38 1 4 5 1
39 1 4 9 1
40 1 4 9 1
41 1 4 9 1
42 1 4 4 0
43 1 4 4 0
44 1 4 4 0
45 1 4 4 0
46 1 4 4 0
47 1 4 4 0
> # find the runs of 'ia'
> z.rle <- rle(x$ia)
> # get the offsets of each sequence
> z.rle$offset <- cumsum(c(1,z.rle$lengths))
> ia4 <- which(z.rle$values == 4)
> for (i in ia4){
+ # set all the saccade values to 0
+ x$saccade[seq(z.rle$offset[i], length=z.rle$lengths[i])] <- 0
+ # set at most the first two to 1
+ x$saccade[seq(z.rle$offset[i], length=min(2, z.rle$lengths[i]))] <- 1
+ }
>
> x
vp trial ia saccade
1 1 1 5 0
2 1 1 5 0
3 1 1 5 0
4 1 1 5 1
5 1 1 5 1
6 1 1 9 1
7 1 1 9 1
8 1 1 9 1
9 1 1 4 1
10 1 1 4 1
11 1 2 5 0
12 1 2 5 0
13 1 2 5 0
14 1 2 5 1
15 1 2 5 1
16 1 2 9 1
17 1 2 9 1
18 1 2 9 1
19 1 2 4 1
20 1 2 4 1
21 1 2 4 0
22 1 2 4 0
23 1 3 5 0
24 1 3 5 0
25 1 3 5 0
26 1 3 5 1
27 1 3 5 1
28 1 3 9 1
29 1 3 9 1
30 1 3 9 1
31 1 3 4 1
32 1 3 4 1
33 1 3 4 0
34 1 4 5 0
35 1 4 5 0
36 1 4 5 0
37 1 4 5 1
38 1 4 5 1
39 1 4 9 1
40 1 4 9 1
41 1 4 9 1
42 1 4 4 1
43 1 4 4 1
44 1 4 4 0
45 1 4 4 0
46 1 4 4 0
47 1 4 4 0
>
On Mon, Aug 3, 2009 at 11:05 AM, Jens Bölte<boelte at psy.uni-muenster.de> wrote:
> Hello,
>
> I have run an eye-tracking experiment for which I now like to analyse the
> saccades. Participants looked from a fixation cross (ia = 5) to the target
> area (ia = 4) in following example of a data frame. ia = 9 stands for
> everything else. A saccade is indicated by saccade = 1. Sometimes the
> saccade just ends before the target area (see below). This is due to the
> parameters that determine a saccade and a fixation and some measurement
> error (accuracy of the eyetracker). I like to include the first two
> no-saccades in a target area into the saccade. The simplest approach, at
> least to my knowledge, would be to replace the value saccade = 0 with
> saccade = 1 for the first two ia = 4 (see the example below). But that is
> beyond my rather limited knowledge in R.
> My data frame is structured as follows (.... stands for multiple rows; just
> deleted for presentation purposes)
>
> vp trial ia saccade (other columns deleted for presentation purposes)
> 1 1 5 0
> 1 1 5 0
> 1 1 5 0
> 1 1 5 1
> 1 1 5 1
> ....
> 1 1 9 1
> 1 1 9 1
> 1 1 9 1
> ....
> 1 1 4 1
> 1 1 4 0
> .....
> 1 2 5 0
> 1 2 5 0
> 1 2 5 0
> 1 2 5 1
> 1 2 5 1
> ....
> 1 2 9 1
> 1 2 9 1
> 1 2 9 1
> ....
> 1 2 4 1
> 1 2 4 1
> 1 2 4 0
> 1 2 4 0
>
> aso. more trials follow (up 72).
> 1 3 5 0
> 1 3 5 0
> 1 3 5 0
> 1 3 5 1
> 1 3 5 1
> ....
> 1 3 9 1
> 1 3 9 1
> 1 3 9 1
> ....
> 1 3 4 0 <- how do I get -> 1 3 4 1
> 1 3 4 0 <- how do I get -> 1 3 4 1
> 1 3 4 0 <- how do I keep -> 1 3 4 0
> .....
> 1 4 5 0
> 1 4 5 0
> 1 4 5 0
> 1 4 5 1
> 1 4 5 1
> ....
> 1 4 9 1
> 1 4 9 1
> 1 4 9 1
> ....
> 1 4 4 0 <- how do I get -> 1 4 4 1
> 1 4 4 0 <- how do I get -> 1 4 4 1 1 4 4 0 <- how do I keep -> 1 4 4 0
> 1 4 4 0 <- how do I keep -> 1 4 4 0
> 1 4 4 0
> 1 4 4 0
> 1 4 4 0
>
> Thanks a lot for any help
>
> Jens
>
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> and provide commented, minimal, self-contained, reproducible code.
>
>
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
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